The World Health Organization has said it’s “very worried” by the latest COVID surge in Europe as more countries consider imposing restrictions.
WHO’s regional director Dr Hans Kluge warned there could be 500,000 further deaths from coronavirus by March if immediate action was not taken, the BBC reported.
Europe has again become the epicentre of the pandemic, accounting for half of global cases and deaths.
As cases rise again, several governments have started to reimpose limits on activity, ranging from Austria's full lockdown to a partial lockdown in the Netherlands and restrictions on the unvaccinated in parts of Germany, the Czech Republic and Slovakia.
Watch: COVID in Europe - Czech infections soar as Austria locks down
Dr Kluge blamed the new wave on several factors, including the winter season, the more transmissible Delta variant and an insufficient level of vaccine coverage.
He said: "Covid-19 has become once again the number one cause of mortality in our region.”
Dr Kluge called for simple measures like mask-wearing, a greater rollout of the vaccine and breakthrough medical treatments for COVID.
He added a discussion should be had around mandatory vaccination but this method should only be the “last resort”.
On Friday, Austria said that in addition to a lockdown, it would require the whole population to be vaccinated from 1 February next year.
Both decisions infuriated many in a country where scepticism about state mandates affecting individual freedoms runs high.
A fourth wave of infections has plunged Germany, Europe's largest economy, into a national emergency, Health Minister Jens Spahn said, warning that vaccinations alone will not cut case numbers.
Germany has said further measures will be decided based on when hospitalisation rates hit certain thresholds.
In France, President Emmanuel Macron has made it clear he thinks high levels of vaccinations should be enough to avoid future lockdowns.
The Netherlands re-imposed some lockdown measures last weekend for an initial three weeks in an effort to slow a resurgence of coronavirus contagion, but daily infections have remained at their highest levels since the start of the pandemic.
The Czech government has approved plans to allow only those who are vaccinated or have recovered from COVID-19 in the past six months to enter restaurants, attend certain events and use some other services from Monday.
Slovakia will impose stricter measures for people who have not been vaccinated against the novel coronavirus amid a surge in infections and hospital admissions that are stretching the health system, Prime Minister Eduard Heger said on Thursday.
Watch: COVID surge in Europe shows 'critical' need to vaccinate millions